1. Field of the Invention
This invention relates to electronic gas and chemical sensors.
2. Discussion of the Related Art
Sensors for gases and chemicals have applications in food processing, agriculture, medicine, and environmental surveillance. Herein, we refer to both gases and chemicals that sensors detect as odors. The applications of odor sensors depend on the sensors"" selectivities, sensitivities, reproducibilities, and reliabilities. Some odor sensors have selectivities and sensitivities that enable both identifying odors and determining the concentrations of identified odor molecules.
Some odor sensors use resistors with resistances that are sensitive to the presence of specific odor molecules. In array-type resistance sensors, the resistances of individual ones of the sensitive resistors react differently to the presence of different types of odors. The resistors generate an array of resistance values that function as fingerprints for identifying various odors.
In one aspect, the invention features an electronic odor sensor. The sensor includes first and second amplifiers, a biasing network, and a device connected to receive the output signals from the first and second amplifiers. The device is configured to correlate the received output signals to the presence or absence of an odor. The first and second amplifiers have respective first and second organic semiconductor layers and are configured to produce output signals responsive to the conductivities of their respective organic semiconductor layers. The conductivities of the organic semiconductor layers are responsive to voltages applied to associated ones of the amplifiers and to the presence of the odor. The biasing network applies the voltages to the amplifiers.
In a second aspect, the invention features an electronic odor sensor. The sensor includes first and second organic field-effect-transistors, a biasing network to cause voltages to be applied to gates of the first and second organic field-effect transistors, and a device connected to receive signals responsive to the drain currents in the transistors. The drain currents the transistors have values responsive to the presence of two odors when voltages are applied to the transistors. The device is also configured to distinguish between the presence of the first odor and the presence of the second odor based on values of the received signals.
In a third aspect, the invention features a process for detecting odors. The process includes absorbing an odor into organic semiconductor layers of an array of amplifiers and measuring output signals produced by the array of amplifiers in response to the act of absorbing. The layers have conductivities that respond differently to absorbing an odor, and the output signals are responsive to the conductivities of the layers. The process also includes determining the identity of the absorbed odor based on the measured set of output signals.